This invention is an improvement of my previously invented explosion proof battery which is the subject of my U.S. Pat. No. 4,529,674 and which is incorporated herein by reference.
The means of that invention serves well to protect the battery from externally ignited gases propagating combustion to the battery cells and thereby causing a dangerous explosion. However, ongoing studies of the battery's performance reveals situations where significant improvement in the battery can be achieved with the addition of new inventive means to overcome the problems associated with these situations.
In large batteries having tens and even hundreds of cells it is possible to have internal ignition sources develop from a number of circumstances, such as faulty workmanship in assembling the battery, faulty materials of construction, damage in handling the battery, and the like. These large batteries, unlike the ordinary automobile battery can still be serviceable with one or a small number of "dead" cells. Heretofore, when ignition reaches or is originated in the interior of the battery the ignition has propagated from cell to cell by way of ignition routes between the cells and as a result not only did a large explosion occur, but many cells of the battery were damaged to the point where it became necessary to remove the battery from service and replace the damaged cells or discard the battery.
Another internally arising battery explosion potential comes about when the battery is tipped to a steep angle or inverted so that the normal gas exit routes are blocked by battery fluid. Such situations can arise in auto accidents, in vehicles that can operate at steep angles, in airplanes flying inverted, and the like. Ordinarily there is sufficient gas space in the cell and the pressure build up is negligible so that no significant hazard is present. However, if the gas escape paths are blocked for a lengthy period of time or there is a sustained heavy electrical load placed on the battery when the gas escape ports are blocked then a hazardous situation is present. First, the ordinary battery will expel battery fluids through the ordinary gas vents of the battery, and if the pressure buildup is great enough an explosion can occur.